The present invention relates to a method for winding electrode foils and separators into a small size capacitor, and more particularly to a method for winding electrode foils in which the relatively short electrode foils and the relatively short insulating papers are wound with a pain of lead wires fixed to the positive and the negative electrode foils respectively being positioned beforehand so as to be precisely opposed to each other.
For example, in a case where short electrode foils several tens of millimeters in length are wound into a small size aluminum electrolytic condenser, it is possible to simplify the apparatus for winding electrode foils and separators by attaching lead wires to the positive and negative electrode foils beforehand at predetermined intervals.
In the manufacture of capacitor elements by superimposing and winding electrode foils and separators or insulating paper, the lead wires for the positive and the negative electrodes must be disposed symmetrically with respect to the center of the capacitor element. An unsymmetrical disposition of the lead wires is undesirable for the following reasons:
(a) The gap between the positive and the negative electrode foils is uneven or unduly large, thereby making the electrical properties of the capacitor element unstable.
(b) The gap between the electrode foil and the separator or insulating paper is unduly large, thereby causing displacement between the electrode foil and the separator and causing a short-circuit.
(c) Subsequent steps of the automatic capacitor assembly operation, such as insertion of rubber packings, are made difficult or unsmooth, leading sometimes to damage of the electrode foils.
Although the above-described problems are caused by the unsymmetrical arrangement of the lead wires, conventional winding methods for small capacitors have not precisely positioned the lead wires on and cut the electrode foils at the precise positions spaced predetermined distances from the lead wires and, accordingly, it has been impossible to wind the foils with the lead wires in a precisely opposed relation. In the conventional methods including, for example, the invention disclosed in Japanese Patent Publication No. 5508/68 entitled "Automatic Capacitor Element Winding Apparatus," the principle interest was only in achieving a uniform winding length of the electrode foils, not in obtaining a uniform position of lead wires attached to the electrode foils. In fact, in the automatic winding apparatus according to the above-identified Japanese Patent Publication, the electrode foils are cut without stopping their movement and it is impossible to cut them with high dimensional accuracy and moreover it is very difficult to position the leading wires accurately.